1. Field of the Invention
The present invention relates to an IP telephone apparatus, an ENUM server, a terminal apparatus and an IP telephone system, particularly to an IP telephone apparatus, an ENUM server, a terminal apparatus and an IP telephone system that provide visual communication.
2. Description of Related Art
With rapid spread of the Internet these days, an IP telephone system draws attention since the system allows low-rate calls to a telephone apparatus in a remote location and free calls between IP telephone apparatuses of subscribers. A protocol “ENUM (Telephone Number Mapping),” provided in RFC2916 (Publication 1) that the IETF (Internet Engineering Task Force) and the ITU-T (International Telecommunication Union-Telecommunication Standardization Sector) have been developing, is used to connect services and resources on the Internet with telephone numbers.
Based on a DNS (Domain Name System) architecture, the “ENUM” protocol retrieves IP addresses or URI's (Uniform Resource Identifier), using telephone numbers converted to meet the E.164 system defined by the ITU-T.
Using a URI set in NAPTR recourse records registered on the ENUM server, an IP terminal apparatus is able to access a variety of resources that the IP terminal apparatus supports. Services taking advantage of the resources include visual communication, proposed by a plurality of companies.
[Publication 1] The first report of ENUM Trial Japan issued by ENUM Trial Japan in May, 2004
However, the visual communication that uses the IP terminal apparatus requires an additional investment in new software and hardware to allow motion image capture and high-speed encoding and decoding. The cost burden on users hampers the growth of visual communication.
It is, therefore, expected to achieve inexpensive visual communication that uses a telephone apparatus, a personal computer and other user-owned properties.